1. Field of the Invention
The present invention relates to a location confirming system, in particular, a location confirming system which is a system performing confirmation of location based upon a presumption measure mutually comparing electric power or amplitude of signals received at the respective receiving station as a system capable of performing location confirming as accurately as possible with a small number of receiving stations. The location confirming system is constructed with a transmitting measure in transmitter and a receiving measure in receiver. For instance, the system can be applied to an indoor wireless communication, movable-body communication, personal communication, and so on.
2. Description of the Prior Art
As for the prior-art, for instance, "An Outline of an Optical message communication System (CANS) and Future Business Development" (Author; Kohji Nagata, Business Communication, '91 Vol. 28 No. 1, pp. 128-135) is one of the prior-art documents. The above document relates to a system employing infrared light rays, and the system comprises an ID pen or a message card carried by respective workers and an optical tranceiver (transmitter/receiver) and an optical sensor both installed on the ceiling. Further, the same performs not only bilateral(two-way)-direction communication by use of the optical transceiver but confirmation (locating) of the residence by use of the optical sensor.
Various systems utilizing an electric wave or infrared light rays have been proposed hitherto, as a location confirming system. In those system, plural receivers are installed indoors on the ceiling at adequate intervals, and the receivers receive a discrimination signal transmitted from an object worker in order to confirm the location of the object worker.
In such conventional system, a method of judgment in which the receivers are distributed such that the signal transmitted from the object worker is received only by one of the plural receivers and thereby the existence of the worker near the receiver has been employed hitherto. However, the receiving directivity of the respective receivers has to be made acute in order to perform location confirming accurately, and nevertheless it accordingly turns out to be necessary to install a large number of receivers at the required locations. For instance, in the system example described in the reference document, the optical sensor employed for confirming location performs transmitting and receiving within the area of a circle with the radius of 1-2 m.
FIG. 23 is a conceptional diagram showing the conventional location confirming system. As shown in FIG. 23, transmitters such as infrared sensors or antennas are installed at several parts of the ceiling on the corridor or the entrance or ceiling of the room. When an object to be sensed, for instance, an office worker approaches to or pass through those sensors or antennas, the signals transmitted from each of the transmitters carried by the worker are received by the receiver.
The location of the object to be sensed is confirmed by reading out the discrimination data among the received signals. Since, in such conventional system, it is an object of the invention to confirm the existence or non-existence of the object (to be sensed) at the location where the sensor or antenna is installed, the distance between the respective receiving stations has to be sufficiently large (separated) such that the signal from the worker can be prevented from being simultaneously received by the respective receivers installed at two places.
Especially, in the case of employing the electric wave, since only very rough location presuming can be done, the system is ill-fitted for confirming location in a wide space such as a large room in the office. On the other hand, in the case of employing the infrared light rays, it is necessary to install a large number of receivers longitudinally and transversely within the area for sensing the object. The above-mentioned matters are the defects of the prior art.